This invention relates to an A.C.-D.C. or D.C.-A.C. converting station (hereinbelow referred to as "D.C." converting station) in a D.C. power transmission. More specifically, it relates to an enclosed D.C. converting station useful for reducing the installing area and simplifying the structure.
Recently, a D.C. power transmission system which has various advantages such as an inexpensive line construction cost as compared with an A.C. power transmission system have been employed in a practical use. An indoor type, an air insulating type or an indoor air cooling type has heretofore been adopted for a thyristor bulb for rectifying alternating current into direct current of devices in a D.C. converting station of this D.C. power transmission system, and the thyristor bulb and control devices belonging to the bulb have been frequently contained in a building.
On the other hand, a thyristor bulb which is cooled by insulating oil or gas has recently been employed in a practical use due to the request of increasing the capacity or raising the voltage. As a result of such a practical use of an enclosed thyristor bulb, the study of the devices in the converting station, i.e., a current transformer for a D.C. instrument, a transformer for a D.C. instrument, a transformer, a reactor, a lightning unit, a disconnecting switch, buses are all enclosed, so-called an enclosed D.C. converting station has been proceeded, and the construction of a test plant and a proving test has also been advanced.
First of advantages of enclosing the D.C. converting station is a point of improving a contamination resistance performance from the external environment of a charger. As a result, the reliability of various devices can be improved. Second of the advantages is a point of shortening an insulating distance by the action of insulating oil or gas, resulting in a reduction of the entire converting station.
Heretofore, in a substation for an A.C. power transmission, the substation is enclosed, and reduced in size by employing gas insulation for electric devices so as to remedy a difficulty of obtaining a site, a public pollution, a contamination, an earthquake, etc. The disposition of the electric devices in the substation is most important in the substation. Periodic inspection and maintenance are conducted mainly for circuit breakers. From this point of view, it is desired to consider the disposition of the devices mainly for the thyristor bulb of the most important device in the D.C converting station.
FIG. 1 is an example of a plan view showing the disposition of devices in a proposed conventional enclosed D.C. converting station, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a circuit diagram of a min circuit of FIG. 1. In FIGS. 1 and 3, characters TR1, TR2 designate transformers, and characters TVG1, TVG2 thyristor bulb group of .+-.250 kV when the converting station of this example is .+-.250 kV. Character V1 to V12 indicate thyristor bulbs which construct the thyristor bulb group. The groups TVG1 and TVG2 are connected in series to form a series connection unit. Characters LA1 to LA12 denote lightning arresters for protecting the thyristor bulbs V1 to V12 against an overvoltage, characters DCR1 and DCR2 D.C. reactors, characters LA13, LA14 lightning arresters of the terminals of the reactors DCR1, DCR2, and characters L2, L1 .+-.250 kV D.C. power transmission lines.
A.C side 3-phase buses R, S, T and U, V, W are disposed perpendicularly, as shown in FIG. 1, at the center in the D.C. converting station. The thyristor bulb V1, V2, V3 and V4, V5, V6 of the thyristor bulb group TVG1 are disposed at both sides of the buses R, S, T. The thyristor bulbs V7, V8, V9 and V10, V11, V12 of the thyristor bulb group TVG2 are disposed at both sides of the A.C. side 3-phase buses U. V, W.
The positive (+) D.C. side bus B4 of the thyristor bulb group TVG2 is disposed to be superposed on the upper position of the A.C. side 3-phase bus U, and the negative (-) D.C. side bus B1 of the thyristor bulb group TVG1 is disposed to be superposed on the upper position of the A.C. side 3-phase bus T (See FIG. 2). The common D.C. side bus B2 and B3 of the positive (+) side and negative (-) side of the thyristor bulb groups TVG1 and TVG2 are respectively disposed linearly to be superposed on the upper positions of the A.C side 3-phase buses R, W.
Disconnecting switches DS1, DS2 are respectively disposed in the course of the D.C. side buses B2, B3. A neutral line N is led substantially in parallel with the D.C. power transmission lines L1, L2 from between the both disconnecting switches DS1 and DS2.
The enclosed D.C converting station constructed as described above is considerably reduced as compared with the gas insulating type D.C. converting station, but still has such a disadvantage to require an extremely large site since the bulb arm units are separated from each other.